1. Field of Invention
This invention relates to valves for adjustable mixing of fluids, especially thermal mixing of water for baths and showers.
2. Prior Art
There are many types of water mixing valves for baths and showers, but each has disadvantages.
The most common arrangement incorporates separate flow valves for hot and cold water, combining the flow path downstream. The user must adjust both valves iteratively to arrive at a desired combination of temperature and flow rate. This is inconvenient and time consuming. The iterative process must be repeated for each change of temperature or flow, discouraging a change of flow rate during showers to save water.
Another type of mixing valve, commonly found in kitchen sinks, has a single lever which controls both mixture and flow. These valves are adjusted iteratively, since there are no reference points for the control. Trial and error must be used to find a desired position in the spherical range of the control handle. The exact full hot position is not certain, so cold water may be wasted while waiting for hot water to arrive. These valves are notorious leakers, probably due to the complex stressing of seals from the three-dimensional motion of the handle.
A shower valve often found in hotels has a single control handle for the hot/cold mixing ratio, which also turns the flow fully on or off. Adjustment is simplified by the lack of graduated flow control. Iterative temperature adjustment is still required, although it is made easier. The tradeoff is waste due to excessive flow. People do not choose such valves for their homes, preferring the ability to adjust the flow low to economize, and high for rinsing and scalp massage.
Time and water is wasted during the adjustment period of shower valves that require iterative adjustment. The total waste is substantial, since this activity is performed every day by many people. As a ballpark figure, assume 100,000,000 baths or showers a day are taken in the U.S., with the following three roughly estimated categories of waste. This invention offers partial savings in the second and third categories, although its main claimed benefit is user convenience.
__________________________________________________________________________ WASTED WASTED SECONDS GALLONS DESCRIPTION __________________________________________________________________________ (a) 20 1 Water in transit from heater to valve (b) 20 1 Iterative temperature and flow adjustment (c) 0 1 Water running while soaping only __________________________________________________________________________ TOTAL DAILY WASTE IN U.S. 1,000,000 man-hours 300,000,000 gallons TOTAL YEARLY WASTE IN U.S. 365,000,000 man-hours 100,000,000,000 gallons __________________________________________________________________________
An auxiliary flow valve can be installed downstream of the water mixing point to provide independent control of the total flow rate. Such a valve is available in some shower heads for temporary shutoff, saving in category C. However, the water is cooler when restarted, due to heat loss while the flow is stopped. Shower heads are generally not adequately leakproof to provide a primary shutoff, so the mixture valves are used, and must be readjusted for each shower.
Such an auxiliary valve can be fully leakproof, and the mixture controls left at their last setting between showers. However, cold water then runs during startup, wasting both water and time.
Another approach is to heat water at its point of use. This is effective and efficient in terms of time, water, and heating energy. However, it is expensive to install a water heater at each point of use, and it requires the skills of both an electrician and plummer. It also adds complexity and priority to maintenance and repair. Improper or damaged installation presents electric shock hazard at its most dangerous site.
Several thermostatic mixing valve designs are recorded in patents, but they are not commonly used in showers, to the applicant's knowledge, possibly due to disadvantages such as those mentioned here for one such valve--inventor Baberg, W. German patent 2802377, 7/1979.
The design of Baberg's mixing valve causes an inherent mixing delay due to the separation of the inlet ports by the valve rotor. The separation of inlet flows persists due to baffling by the rotor and thermostat connection parts, which prevents thorough mixing prior to the thermostat element. Thus, uneven mixing may complicate calibration of the thermostat due to thermal eddies. Eddies are unpredictable due to variability in inlet pressures, baffle variation with valve position, and sample variation in manufactured valves. The present invention mixes immediately in the throat of the mixing valve, and provides thorough mixing prior to the thermostat.
Another disadvantage in Baberg's valve is that hydrodynamic pressure is not neutral against the rotor. Inlet flow impinges on the rotor and thermostat connection parts, causing rotational moment on the rotor. This is detrimental to calibration. The opening of an inlet causes dynamic pressure on the rotor which tends to re-close the inlet. This in turn reduces flow, allowing the inlet to reopen, and so on. This is likely to result in oscillations of the rotor, requiring damping. The present invention is designed with neutral rotational effect on the rotor from the inlet flows.